The invention relates generally to computer systems for converting a higher resolution image to a lower resolution image for display on a computer display apparatus generally of the cathode-ray tube type or other types of display apparatuses (e.g. liquid crystal display). More specifically, the invention relates to a system utilizing weighted averaging of pixel values to convert from a higher resolution image to a lower resolution image.
Computer systems are capable of displaying graphics using pixels, which are dots generated on a video screen, such as a computer monitor. A typical computer usually has one output which can generate an image of a certain resolution (e.g. 512.times.256). This video technology is well known and described in various textbooks and references including Raster Graphics Handbook, produced by Conrac Division, Conrac Corporation, (ISBN: 0-9604972-0-X; Library of Congress Catalog No.: 80-69450). Often, a computer has a video output, which can provide a higher resolution image and a lower resolution image. However, the lower resolution image is independently created and is not derived from or converted from the higher resolution image.
The present invention provides for a means (e.g. a pixel averaging means) for converting from the high resolution image to the low resolution image and thus avoids the need for independent methods of creating the lower resolution image.
The present invention includes a special memory means which is a dual clock shift register; this memory means allows for the outputting of the converted (lower) resolution image at a different clock rate than the input of the high resolution image into the conversion system which converts between the high and low resolution images.
In a typical computer system which displays graphics, the pixel values are stored in an image memory which is a bit map of the screen, as is well known in the prior art. The pixel values are read out from the image memory, such as a "frame buffer", to produce the image on the screen. The pixels are typically integers represented by digital values from 0 to an upper limit, for example, 255. As is well known in the art, the digital values are converted to analog signals through digital to analog conversion circuitry, which are used to generate the image. Thus, for example, a pixel having a value of 0 is completely dark while a pixel having a value of 255 produces the brightest possible spot on the screen at the location of the pixel. If the display is an RGB (Red-Green-Blue) color display, each of the three components, red, green and blue, has its own pixel value to indicate the intensity of the particular component. Thus, for example, if the component is the red (R) component then the pixel value 255, in the present example, would be the reddest red possible. If the pixel averaging system of the invention is used with an RGB color display, there will be three pixel averaging means, each of which averages one of the three color components.
It is an object of the present invention to provide a system and process for converting the pixels in a high resolution image to pixel values in a lower resolution image through a pixel averaging means which calculates and outputs weighted averages based on the pixels in the high resolution image.
It is a further object of the invention to provide a way to view a high resolution image on a lower resolution monitor or screen by averaging pixels in the high resolution image. Moreover, it is an object of the invention to provide a system and architecture for averaging the pixels from the high resolution image to the lower resolution image. Moreover, it is an object of the invention to provide a system and architecture for averaging the pixels on a single integrated circuit (IC) chip for each component in a RGB color system.
Furthermore it is an object of the invention to provide a system and architecture for averaging a 3.times.3 group of pixels to a single pixel in a low resolution image. It is also an object to provide a system and architecture to average a group of 2.times.2 pixels to a single pixel for display on a low resolution screen.
It is also an object of the invention to provide a memory means in the form of a dual clock shift register which can output information for the low resolution image at a different clock rate than the clock rate at which it receives converted pixel values.